1. Field of the Invention
The present invention relates to a device having a part actuated via a drive apparatus, preferably a handling device having an actuated positioning part or a press having a press ram actuated by the drive apparatus.
2. Related Prior Art
Devices of this kind are commonly known from the prior art; they serve as presses, for example on the one hand for shaping objects and on the other hand for fitting together workpieces that must be assembled under pressure. The handling devices used in particular in the press sector are used, for example, to position under the press the workpieces that are to be fitted together.
On the one hand fluid-actuated piston-cylinder units, and on the other hand spindle drives that are actuated via an electric motor, are known as the drive apparatus for devices of this kind.
Especially in the case of presses that must perform a very high number of press strokes during their service life, it is inherently necessary to lubricate the moving parts. In the case of spindle drives, for example, it is known that if they are not continuously lubricated during operation, they fail due to insufficient lubrication after approximately 500,000 strokes.
In spindle drives of this kind which have either a driven, axially nondisplaceable threaded spindle or a driven, axially nondisplaceable spindle nut, lubrication of the threads between the threaded spindle and spindle nut is, however, of very complex configuration, especially in presses, since this region in the interior of the press is poorly accessible. For this reason, it is impossible to use such spindle drives in so-called electric presses if such electric presses are to be operated in continuous service.
In view of the above, it is an object of the present invention to improve the device mentioned at the outset in such a way that with a simple design, continuous operation is possible and susceptibility to malfunction is reduced.
In the case of the device mentioned at the outset, this object is achieved according to the present invention in that a dosing system that can be actuated by the drive apparatus is provided for lubricating at least the drive apparatus.
The object underlying the invention is completely achieved in this fashion.
Specifically, the inventors of the present application have recognized that it is possible to equip, for example, a press of this kind with an automatic dosing system that can be actuated by the drive apparatus itself. This feature is advantageous in terms of design especially because lubrication is not achieved by way of an additional drive system or an additional pneumatic/hydraulic system, which would increase the design outlay, cost, and especially the susceptibility to malfunction. Both cost and susceptibility to malfunction would be increased even further with a separate drive system because of the additional monitoring elements for a separate drive system for this dosing system, and the additional control outlay.
Although the additional dosing system requires in all cases a greater design outlay than is necessary, for example, for presses without a dosing system, it is nevertheless possible in this case, because the usual drive apparatus that is already provided for the press ram can also be used to actuate the dosing system, to use the control system provided in any case for this so-called servo axis to control the lubrication or greasing system as well, so that no additional design actions are necessary for actuation and control of the dosing system.
It is preferred in general if the drive apparatus comprises a spindle drive as well as an electric motor for actuating the spindle drive, the spindle drive preferably comprising a threaded spindle, driven by the electric motor, that is mounted in axially nondisplaceable fashion, as well as a spindle nut that is axially displaceable via the threaded spindle but is radially nonrotatable, and is joined to the actuated part.
This feature is advantageous in terms of design: for example, presses with a stationary threaded spindle are generally of simpler design than presses having an axially nondisplaceable spindle nut.
It is furthermore preferred if the dosing system comprises a lubricant cylinder that can be filled with lubricant, as well as a greasing piston, for ejecting the lubricant, that projects into said cylinder""s interior and can be actuated via the drive apparatus.
The advantage here is that the dosing system selected is extremely simple: the greasing piston must simply be pushed by the drive apparatus into the lubricant cylinder, a portion of the lubricant being delivered to the corresponding lubrication points with each inward push. Actuation of the greasing piston can be accomplished, for example, by the fact that the drive apparatus is selectably joined via a coupling to an advance linkage for the greasing piston. The greasing piston can then effect lubrication during a normal working stroke, provided it is coupled to the drive apparatus.
On the other hand, it is preferred if the greasing piston is in working engagement with the spindle drive as a function of the axial position of the actuated part.
The advantage here is that coupling is accomplished, so to speak, via the axial shifting of, for example, the press ram, so that no additional coupling elements, etc. are required.
It is further preferred if the greasing piston comes into contact with the spindle nut when the actuated part is in an axial position outside its working stroke.
The advantage here is that by way of a simple displacement of the spindle nutxe2x80x94and thus of, for example, the press ramxe2x80x94out of the actual region of the working stroke, the spindle nut comes into contact with the greasing piston and can then push the latter, controlled by the drive apparatus, progressively into the lubricant cylinder. This means that with the exception of a greasing piston, which can be actuated, for example, via a wedge drive train via the spindle nut, no major design changes need to be made to, for example, the press.
On the other hand, it is preferred if the lubricant cylinder is provided preferably concentrically with the threaded spindle, preferably on the side of the spindle nut remote from the press ram, and the greasing piston is arranged preferably concentrically with the threaded spindle between the lubricant cylinder and the spindle nut.
This feature is also advantageous in terms of design, since no further linkage is necessary between the greasing piston and the spindle nut. To perform a lubricating operation, the spindle nut simply needs to be moved upward, by corresponding rotation of the threaded spindle, until it comes indirectly or directly into contact with the greasing piston, and correspondingly pushes the latter farther into the lubricant cylinder.
If the lubricant cylinder and the greasing piston are arranged concentrically with the threaded spindle, they can be arranged above the spindle nut, for example in the tube which guides the press ram, so that there is also no great need for installation space for the dosing system.
It is preferred in this context if there is provided in the greasing piston a lubricant conduit that connects the interior space of the lubricant cylinder to a lubrication orifice in the spindle nut and opens out in the region of the threaded spindie, when the nut is in contact with the greasing piston.
This feature is also advantageous in terms of design: the reason is that no lubricant hose or the like needs to be installed from the lubricant cylinder to the lubrication point; instead the lubricant is conveyed downward by way of the greasing piston itself, and passes through the lubrication orifice in the spindle nut directly into the thread region between the spindle nut and threaded spindle. This feature as well therefore once again greatly reduces the design requirements.
It is preferred in this context if there is provided in the press ram a discharge orifice for used lubricant that opens below the spindle nut into a space between the spindle nut, threaded spindle, and press ram, and connects that space to a reservoir for used lubricant.
This feature is also advantageous in terms of design: the reason is that there is located in the space, so to speak, a comoving lubricant reservoir that ensures sufficient lubrication in the thread region as the spindle nut travels along the threaded spindle, and on the other hand collects the used lubricant. When fresh lubricant is then pressed between the threaded spindle and spindle nut above this space, the used lubricant is pressed out of the space into the reservoir, where it can be removed and disposed of in environmentally compatible fashion.
This feature also makes a substantial contribution to increasing the operating reliability of the new press, since used grease does not accumulate at inaccessible locations in the press, where it can result in operating malfunctions due to corresponding hardening.
It is further preferred if the discharge orifice opens into a pocket that is provided on the press ram on the latter""s outer side that is guided in a tubular element, an orifice being provided in the tubular element and connecting the pocket to the reservoir, the pocket preferably having, in the axial direction of the threaded spindle, an extension that corresponds approximately to the maximum stroke of the greasing piston in the lubricant cylinder.
The advantage here is that provision is made, with a simple design, for used lubricant to be disposed of via the pocket into the reservoir in all the axial positions of the press ram in which a lubricating operation takes place. When the lubricant cylinder is filled, i.e. when the greasing piston is in its axially lower position, the orifice in the tubular element is arranged in the upper region of the pocket; the pocket then migrates farther upward, with reference to the orifice, from one lubricating operation to the next, until the orifice ultimately is located at the lower end of the pocket.
The size of the lubricant cylinder can moreover be selected, without complex design actions, in such a way that when operated 16 hours a day, the lubricant cylinder does not need to be refilled with lubricant for approximately three years. The inventors of the present application have recognized that because of the concentric arrangement of the lubricant cylinder above the spindle nut but inside the tubular element guiding the press plunger, so much room is available that this quantity of lubricant can be accommodated in a kind of reservoir. It is thus not absolutely necessary, however, to provide externally accessible lubricating points for filling the lubricant cylinder; this reservoir can instead be refilled during a maintenance operation, required in any event within three years, for which purpose the press must be dismantled. Further design advantages also result, however, from the aforementioned fact that an external refilling capability can be dispensed with. On the other hand, this reservoir can of course also be refillable via a lubrication nipple, through which both the initial lubricant quantity and also, later on, further lubricant can be conveyed.
In general, it is preferred if the reservoir comprises a cassette that is arranged on a housing element of the new device in such a way that it can be removed from the outside, preferably without tools.
The advantage here is that provision is made for disposal of the used lubricant with the simplest possible design.
Lastly, it is also preferred if an O-ring is provided between the lubricant conduit and the lubrication orifice in the spindle nut.
The advantage here is that during the lubricating operation, the lubricant in fact passes into the lubricating orifice and from there into the thread region between the threaded spindle and spindle nut, and is not pushed out to the side.
It is understood that the features mentioned above and those yet to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation, without leaving the context of the present invention.